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Abstract As-cast and as-extruded Mg- x at% Co-6 at% Y (x = 0, 1, 2, 4) alloys were prepared. Their tensile strengths and microstructures were examined by using a WDW-200E material testing machine, X-ray diffractometer (XRD), optical microscope (OM), scanning electron microscope (SEM) and transmission electron microscope (TEM). The tensile strength of the as-cast Mg- x at% Co-6 at% Y (x = 0, 1, 2, 4) alloys reached the peak value of ~246 MPa with the addition of 1 at% Co. Additionally, the tensile strength of the as-extruded Mg- x at% Co-6 at% Y (x = 0, 1, 2, 4) alloys reached the peak value of ~369 MPa with the addition of 1 at% Co. The long-period stacking-ordered (LPSO) phase played a highly important role in the strengthening mechanism of the as-cast and as-extruded Mg- x at% Co-6 at% Y (x = 0, 1, 2, 4) alloys. [ABSTRACT FROM AUTHOR]

The effect that twin activity in Magnesium alloys has in both local and global strain is investigated in this article. The need to investigate this effect is related to difficulties in associating the spatially varying twinning with both plasticity and failure of this particular class of alloys. To address this need, mechanical testing both inside and outside the Scanning Electron Microscope was conducted and it was coupled with Digital Image Correlation (DIC) deformation and Electron Backscattered Diffraction (EBSD) texture measurements. In addition volume recordings of Acoustic Emission (AE) and surface measurements of microstructural changes were used to further complement the in situ tracking of twinning activity throughout monotonic and cyclic mechanical loading experiments. The definition of appropriate monitoring regions allowed the direct correlation of evolving twin activity with associated deformation in Magnesium alloys, for the first time to the authors’ best knowledge, from which twinning contributions to strain localizations were computed. [ABSTRACT FROM AUTHOR]

Three kinds of high-performance as-extruded Mg-Gd-Zn-Zr alloys were successfully prepared by controlling Zn and Gd contents and atomic ratio. The microstructure, mechanical properties and corrosion resistance of the three alloys were studied by optical microscope (OM), scanning electron microscope (SEM), X-ray diffractometer (XRD), electron backscattering diffraction (EBSD), tensile-compressive experiment and electrochemical experiment. The results showed that the coarse grains and continuous second phase of as-cast alloys were refined and broken after hot extrusion, and the main components were α-Mg, W–Mg 3 Gd 2 Zn 3 , I–Mg 3 Zn 6 Gd and MgZn 2 phases. The mechanical properties and corrosion resistance tests revealed that the as-extruded GZ22 alloy had the highest ultimate tensile strength (UTS) of 362 ± 6 MPa and the lowest corrosion rate of 0.94 mm/year, which was attributed to the fine grains and a small amount of dispersed second phase. The strength of as-extruded GZ56 alloy decreased due to excessive hard and brittle W-phase. Meanwhile, a large amount of second phase content made the alloy had the lowest corrosion resistance. In addition, the as-extruded GZ26 alloy with high Zn/Gd atomic ratio had good comprehensive mechanical properties, and its UTS and elongation (EL) were 332 ± 3 MPa and 24.5 ± 0.6%, respectively. The unique feature of this alloy was that weak texture intensity led to good tension-compression yield symmetry, and its corrosion resistance was second only to that of the as-extruded GZ22 alloy. [ABSTRACT FROM AUTHOR]

The effects of four different hot extrusion processes on the microstructure, texture, and mechanical properties of Mg–5Li–3Sn–2Al–1Zn alloys were investigated with the help of optical microscope (OM), scanning electron microscope (SEM), transmission electron microscope (TEM) and electron backscatter diffraction (EBSD) techniques. The results show that the magnesium alloy experienced dynamic recrystallization during the hot extrusion processes, the grain size was significantly refined compared with that of the cast alloy, and the mechanical properties of the alloy were significantly improved. After the 105° forward-parallel channel extrusion process, the alloy exhibited optimal strength and plasticity with 178 MPa, 270 MPa, and 21.03% for tensile yield strength, ultimate tensile strength, and elongation, respectively, which were 61.8%, 44.4%, and 134.4% higher compared to the homogeneous state. The increase in strength is attributed to fine grain strengthening, while the significant increase in plasticity is due to the weakening of the basal texture and the improved coordination of plastic deformation of the magnesium alloy following grain refinement. • Hot extrusion tests were conducted at a lower temperature (250℃) and extrusion ratios (2.78/4). • Four different one-pass extrusion processes were carried out and find the optimal process. • Mg-Li alloys with good strength and plasticity were successfully prepared. • The increase in strength and plasticity of the alloy is attributed to grain refinement and weakening of the texture. [ABSTRACT FROM AUTHOR]

The failure behavior of high pressure die casting AZ91D magnesium alloy during both tensile and fatigue tests was studied in situ by using scanning electron microscope. Attention was focused on the role of microstructure played in crack initiation and propagation. Results showed that the defects in castings, including gas pore, shrinkage pore and defect band, were the crack initiation sources. In tensile test, the crack propagated in a combination of intergranular and transgranular modes, and the specimen fractured by connecting defects at the section with minimum effective force bearing area. In fatigue test, the crack propagated in a transgranular mode at specific crystalline planes. When the crack was in contact with the β-phase, the crack would pass through, and fracture the network β-phase, whereas bypass the island β-phase by detaching it from the surrounding α-Mg grains. Besides, defects in front of the crack would act as the secondary crack initiation sources, from which new cracks would initiate and propagate. With the propagation of the fatigue crack, the actual maximum cyclic stress would increase to the fracture stress of the left cross section and lead to the final fracture of the specimen. [ABSTRACT FROM AUTHOR]

Microstructures and mechanical properties of Mg-3.5Y-2.5Nd-0.5Zr alloy under various heat treatment conditions were investigated by optical microscope (OM), scanning electron microscope (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), micro-hardness tests and tensile tests. The results showed that the as-cast alloy was mainly consisted of α-Mg, Mg 41 Nd 5 , Mg 24 Y 5 and β′(Mg 14 Nd 2 Y) phases. After solution treatment at 798 K for 4 h and subsequent aging at 498 K for 34 h, the alloy obtained the remarkable mechanical properties and the ultimate tensile strength, yield strength and elongation were 301 MPa, 202 MPa and 6.9%, respectively. The super tensile properties were mainly attributed to a high volume fraction of fine β′′ and β′ phase which coexisted together in the matrix. Peak-aged at a relatively high temperature, such as 508 K or 523 K, the coarse β′ phase led to a strength decline. [ABSTRACT FROM AUTHOR]

Mg-xAl alloys (x = 3–12 wt%) were prepared by high pressure solidification. The microstructure of the alloys was studied using Scanning Electron Microscope (SEM) and Electron Backscatter Diffraction (EBSD), and the strengthening mechanism was analyzed in combination with the compressive properties of the experimental alloys. Furthermore, the grain boundary segregation of Al solute was investigated by experiments and first-principles calculations. For the Mg-xAl alloys solidified under atmospheric pressure, the microstructure will be a single solid solution when the Al content of the alloy is less than 5 wt%. However, for the Mg-xAl alloys solidified under 4 GPa pressure, the microstructure will always ba e single solid solution when the Al content of the alloy is less than 12 wt%. Moreover, the segregation of Al solute with a high concentration gradient can be observed at plenty of grain boundaries (area fraction is as high as 46%), because α-Mg dendrites are significantly refined under high pressure. In addition, many Al atoms are dissolved in the α-Mg matrix owing to high pressure. On this basis, it is found that grain boundary segregation of Al solute can decrease the grain boundary energy, and increase the bonding strength of grain boundaries. As a result, the Mg–Al alloys solidified under high pressure have superior compression properties. The compression strength of the Mg–9%Al alloy and the Mg–12%Al alloy solidified under 4 GPa is as high as 458 MPa and 490 MPa respectively, the alloys retain superior plasticity simultaneously. [ABSTRACT FROM AUTHOR]

The thermodynamic stability of intermetallic compounds formed by most conventional alloying elements in Mg alloys is not high, resulting in the poor heat resistance of Mg alloys. Although rare earth (RE) compounds have superior thermal stability, the melting point of Al-RE compounds is generally higher than that of Mg-RE compounds. Therefore, in-depth exploration of the influence mechanism of RE compounds on the heat resistance of Al-containing Mg alloys is necessary. In this work, the thermodynamic stability of the might exist precipitates in Mg–Al–Zn–Mn–Y alloys was analyzed using first-principles calculations and verified via scanning electron microscope (SEM), X-ray diffraction (XRD), energy dispersive spectrometer (EDS), and other experimental methods. Based on their results, the precipitation sequence of the key RE precipitates was deduced. Furthermore, it was investigated whether the preferentially precipitated precipitates could serve as the nuclei of primary α-Mg based on the mismatch theory. Consequently, the refinement mechanism of Y on Mg alloys was elucidated. Besides, the complex alloying reactions in the multi-elemental Mg alloy system were simplified using the electronegativity theory and the Al–Y, Mg–Y, Mg–Al binary phase diagrams, and the strengthening mechanism of Y on Mg alloys was elucidated eventually. The results indicated that the preferentially precipitated granular Al 8 Mn 4 Y and Al 2 Y prevented Mg 17 Al 12 from forming a network structure, and a reinforced structure was formed in which the modified Mg 17 Al 12 particles were mixed with the newly formed granular Al 8 Mn 4 Y and Al 2 Y. Tensile tests and fracture analyses indicated that the reinforced structure improved the mechanical properties of the alloy both at room and elevated temperatures. [ABSTRACT FROM AUTHOR]

The effects of silicon carbide (SiC) dimensions on the microstructure and mechanical properties have been investigated by comparing SiC nanowires (SiC nw) reinforced Mg–2Zn-0.1Y(ZW20) matrix composite with the other two composites reinforced by nano-SiC (SiC np) and submicron-SiC (SiC sp) particles. Three kinds of 0.3 wt% SiC reinforced ZW20 matrix composites (SiC nw /ZW20, SiC sp /ZW20, SiC np /ZW20) were successfully fabricated by ultrasonic assisted with semi-solid stirring cast followed extrusion. The microstructures of the three composites were analyzed by Scanning Electron Microscope (SEM) equipped with Energy Dispersive Spectroscopy (EDS), Transmission Electron Microscope (TEM), X-Ray diffraction (XRD) and optical microscope (OM). Then, the tensile test was performed to unravel the mechanical properties of composites. The results showed that relatively complete dynamic recrystallization (DRX) occurred in the three composites generating plentiful fine grains, the second phases proven be MgZn 2 phases by EDS and XRD precipitated near grain boundaries and SiC. Among the three composites, the average grain size of SiC nw /ZW20 was the finest (only 0.37 μm), which was mainly ascribed to the fact that one-dimensional SiC nw could hinder the growth of grains more effectively by twisting along grain boundaries. And the most complete recrystallization occurred in SiC np /ZW20 due to the maximum number of SiC np. Moreover, the volume fraction of precipitates in SiC nw /ZW20 was ∼50% more than that of SiC sp /ZW20 and SiC np /ZW20, relevant with more nucleation sites contributed by SiC nw. Accordingly, the microstructure given by different dimensions of SiC led to the improvements of yield strength (YS) and ultimate tensile strength (UTS). The synergy of fine-grain strengthening from DRXed grains, dislocation strengthening caused by hot deformation and Orowan strengthening originating from precipitations and SiC may primarily account for the high YS, over 440 MPa. • The effect of SiC dimensions on the microstructure was discovered in three SiC/ZW20 composites. • Low temperature extrusion was achieved in three SiC/ZW20 composites. • The strengthening mechanism in three SiC/ZW20 composites was clarified. • The three SiC/ZW20 composites exhibited YS of 430–500 MPa and UTS of 440–510 MPa. [ABSTRACT FROM AUTHOR]

The compressive creep property of Mg-4Al-RE (AE41) alloys is investigated using a homemade compressive creep device. The microstructure of as-cast and post-crept AE41 alloys is observed by scanning electron microscope (SEM), and the precipitation phases in the alloys are analyzed by X-ray diffraction (XRD) and energy dispersive spectrometry (EDS). The results show that the compressive creep rates of AE41 alloys are decreased with increasing duration in the primary creep stage, and the steady state compressive creep rates are decreased with increasing calcium and strontium concentrations. The steady state compressive creep rate of AECJ411202 alloy is 1.36721x10=sup=-7=/sup=mm/s that is 8.34 times lower than that of AE41 alloy. The poor compressive creep resistance of AE41 alloys is caused by the softening of β-Mg=sub=17=/sub=Al=sub=12=/sub= phase. The compressive creep resistance of Mg-Al-RE-Ca and Mg-Al-RE-Ca-Sr alloys is improved by the grain refinement, and the granular Al=sub=2=/sub=Nd, bone (Mg, Al)=sub=2=/sub=Ca and fish-bone Al=sub=4=/sub=Sr hindering the dislocation climbing and grain boundary sliding. [ABSTRACT FROM AUTHOR]

The mechanical behavior of an extruded magnesium–manganese alloy containing 1wt% of neodymium (MN11) has been investigated at temperatures ranging from room temperature to 400°C at both quasi-static and dynamic rates. Conventional ex-situ tests, carried out in compression along the extrusion axis (EA), have been combined with in-situ tests in a scanning electron microscope (SEM) in order to elucidate the effect of a rare earth (RE) addition on the dominant deformation mechanisms. An unusually large activity of twinning was observed at room temperature in a wide range of quasi-static rates. Furthermore, the twinning activity has been found to increase at temperatures around 250°C, where clear signs of dynamic strain aging (DSA) are also apparent. The enhanced twinning activity compared to conventional Mg alloys, not containing RE elements, is attributed to an increase in the critical resolved shear stress of basal slip (CRSSbasal) due to the presence of intermetallic RE-containing particles and to the Nd atoms in solid solution. The surprising decrease of the twinning activity at dynamic rates (∼103 s−1) may be explained by a decrease in the CRSSbasal as the intermetallic RE-containg particles and the Nd solid solution strengthening become less effective with increasing strain rate. [ABSTRACT FROM AUTHOR]

Abstract: Microstructures and mechanical properties of Mg–8Gd–4Y–Nd–Zn–3Si alloy were systematically investigated using OM, SEM, XRD, TEM, hardness measurements, tensile and resonance test. The as-cast microstructure consists of α-Mg, Mg3(GdYZn), Mg12(GdY)Zn, Mg2Si, Gd5Si3 and YSi2 phases. The long period stacking ordered (LPSO) structure is found in the as-cast sample, which disappears after solution treatment. The mechanical properties of the extruded-T5 alloy are as follows: Young''s modulus E=58.5GPa, yield tensile strength σ 0.2=328MPa, ultimate tensile strength σ b=386MPa and elongation δ=5.9%. The high Young''s modulus of the alloy is attributed to the existence of Mg2Si, Gd5Si3 and YSi2 compounds with high Young''s modulus. The weakening of age hardening response is ascribed to the formation of vast Gd5Si3 and YSi2 compounds, which consumed plenty of rare earth atoms in the matrix and decreased the amount of β″ and β′ precipitates. [Copyright &y& Elsevier]

Abstract: Mg–Zn–Y quasicrystal alloy (QA) particles reinforced composite was prepared using an adscititious method, and characterized using scanning electron microscope (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and tensile testing technique at room temperature. Experimental results indicate that α-Mg columnar dendrite gradually becomes fine equiaxed dendrite and ellipsoidal cellular dendrite as more Mg–Zn–Y QA particles are added into the matrix alloy. Thread-like Mg24(Gd,Y)5 phases and rod-like Mg5(Gd,Y) phases are replaced by lamellar Mg24(Zn,Gd,Y)5 compounds and granule Mg3Zn6(Y,Gd) quasicrystal I-phases. The ultimate tensile strength and yield strength of the composite increase by about 45MPa and 20MPa respectively when the amount of QA particles added increases from 3% to 15%. It can therefore be concluded that the microstructure and mechanical properties of Mg–8Gd–3Y alloy can be improved by adding QA particles. [Copyright &y& Elsevier]

Abstract: Microstructure evolution of adiabatic shear bands (ASBs) in AM60B Mg alloy impacted by a GCr15 projectile at a velocity of 500ms−1 was studied through optical microscope (OM), scanning electron microscope (SEM) and transmission electron microscope (TEM). The results show that the deformed and transformed bands were formed around the crater, and the transformed bands under different etchants presented different responses, which indicated that the etching color to distinguish transformed bands was inaccurate. The ultrafine and equiaxed dynamic recrystallized grains in the transformed bands were confirmed, and twinning-induced rotational dynamic recrystallization mechanism was proposed to be responsible for the formation of the ultrafine grains in the bands. Microhardness measurements show that the microhardness in the bands was two times higher than that of the matrix, which should be attributed to the strain hardening and grain refining. [ABSTRACT FROM AUTHOR]

Abstract: Deformed microstructure and mechanical properties of AM60B magnesium alloy under hypervelocity impact at a speed of 4kms−1 were studied through optical microscope (OM), scanning electron microscope (SEM), transmission electron microscope (TEM) and indenter technique. The results show that the deformed microstructure below the crater can be classified as three zones, i.e. dynamic recrystallization zone, high density deformation twin zone and low density deformation twin zone. The refined and equiaxed recrystallized grains adjacent to the crater were formed, which should be attributed to the twining-induced dynamic recrystallization mechanism. The , deformation twins are confirmed through selected area electron diffraction (SAED) technique. The microhardness and yield strength in the deformed microstructure zone near the crater are much higher than that of the matrix, which should be attributed to strain hardening and grain refining. [Copyright &y& Elsevier]

Abstract: The effects of Cu additions (0.5–2.0wt.%) on the microstructure and hardness of Mg–5Li–3Al–2Zn alloy were studied. Optical microscope, scanning electronic microscope, X-ray diffraction and energy dispersive X-ray spectroscope were employed to study the microstructure of the alloys. Results show that, as the Cu addition increases, the AlCuMg phase exists in the alloy. This phase can partially restrain the formation and growth of AlLi phase. The Brinell macrohardness of the as-cast alloys increases with the increase of Cu content. The Vickers microhardness of the phases of as-cast alloy was measured to analyze the strengthening mechanisms. [Copyright &y& Elsevier]

Abstract: Dry sliding wear tests were performed on a hot extruded ZE41A magnesium alloy using a pin-on-disc (EN32 steel) configuration. Wear rates were measured in a load range of 30–150N, sliding velocity range of 0.5–2.5m/s at a constant sliding distance of 1500m. Microstructures of worn surfaces were characterized by scanning electron microscope (SEM) and energy dispersive spectrometer (EDS). Wear maps were drawn. An empirical wear transition map has been constructed to delineate the conditions under which severe wear and ultra severe wear initiated. The dominant wear mechanisms in each wear regime were identified and classified in a wear mechanism map. [Copyright &y& Elsevier]

Abstract: Microstructures and mechanical properties of Mg–7Y–4Gd–1.5Zn–0.4Zr alloy in the as-cast, as-extruded and peak-aged conditions have been investigated by using optical microscope, scanning electron microscope, X-ray diffraction and transmission electron microscope. The results show that optimal mechanical properties of this alloy are obtained when it was aged at 220°C. The values of the ultimate tensile strength and yield tensile strength are 418 and 320MPa, respectively. The age hardening response decreases with increasing ageing temperature because the β′ phase gets coarse as ageing temperature increases. [Copyright &y& Elsevier]

Abstract: Three kinds of magnesium alloys AZ113, X7 and X20 were prepared by the method of smelting and extruding. The microstructure of three magnesium alloys was observed by both optical microscope (OM) and scanning electron microscope (SEM). The phase composition and elements distribution were confirmed by X-ray diffraction (XRD) and energy dispersive spectroscopy (EDS), respectively. X-ray photoelectron spectroscopy (XPS) was employed to investigate the chemical states of elements and determined the composition of oxidation film on the surface. The elevated temperature tensile strength was carried out at the temperature of 250°C. The results showed β-Mg17Al12 phase in magnesium alloys was refined by the addition of Ca, but the phase composition did not change. The tensile strength of magnesium alloys was enhanced obviously at elevated temperature, which was attributed to solid solution of Ca in the β-Mg17Al12 phase that led the thermally stable of β-Mg17Al12 phase to be improved. The antioxidant properties of X7 and X20 alloys at elevated temperature were improved by the addition of Ca, which led the complex oxidation film CaO·MgO to be formed on the surface of alloys. [Copyright &y& Elsevier]

Abstract: An investigation of the fatigue crack propagation (FCP) behavior of the as-extruded magnesium alloy AZ80 was made by means of the constant load amplitude fatigue test, scanning electron microscope (SEM), transmission electron microscopy (TEM) and Auger electron spectroscopy (AES). The results demonstrated that loading frequency had a significant influence on fatigue crack propagation rate, and it increased with a decrease in loading frequency and an increase in load ratio. Crack closure induced by plasticity rather than oxide film might play a predominant role in fatigue crack propagation. The coalescence of the microvoids was proposed to be the mechanism of fatigue crack propagation of the extruded magnesium alloy AZ80. [Copyright &y& Elsevier]

Although the amount of Cr in chemical composition of 7xxx series alloys is usually less than 0.1 wt%, it significantly affects the properties and microstructural evolutions during thermo-mechanical processing of these alloys. In this study, the effect of the elimination of Cr on the microstructural evolutions of ECO-7175 alloy during hot deformation is investigated. ECO-7175 alloys with and without Cr were subjected to hot compression at 350, 400, 450, and 500 °C and strain rates of 0.001, 0.01, 0.1, and 1 s−1. The microstructural evolutions of the alloys were studied through Optical Microscopy, Scanning Electron Microscopy, Scanning Transmission Electron Microscopy, and Electron Backscatter Diffraction analysis. Scanning Electron Microscope and Scanning Transmission Electron Microscope observations revealed that removal of Cr eliminates ε precipitates from microstructure of the alloy. The elimination of ε precipitates that act as Zener pining agents were found to affect the kinetics of static recrystallization of the initial materials during the preheating and mechanisms of dynamic restoration of the alloy during hot deformation. Although the microstructural observations revealed that continuous dynamic recrystallization and dynamic recovery were the main restoration mechanisms for both alloys, Electron Backscatter Diffraction analysis showed that the finely dispersed ε precipitates impede movement and rearrangement of dislocations and slow down the rate of dynamic recovery and continuous dynamic recrystallization in the Cr-containing samples. • Removal of Cr from affected the microstructure of ECO 7175 significantly. • Removal of Cr resulted in removal of e precipitates that act as Zener pining agents. • The number of second phase and grain boundary precipitates decreased significantly with the removal of Cr. • The presence of ε precipitates reduces the growth rate of DRXed grains. [ABSTRACT FROM AUTHOR]

Slip/twinning activity and theoretical critical shear strengths (τ max) during room-temperature tensile deformation of as-extruded pure Mg and Mg-1wt.%Y sheets were investigated quantitatively via electron back-scattered diffraction (EBSD), scanning electron microscope (SEM) and first-principles calculation. Slip trace analysis results indicated the relative frequency of the active slip modes transformed from basal slip (100%) for pure Mg, to basal slip (84.8%), prismatic slip (9.7%) and pyramidal slip (5.5%) for the alloy. The proportion of grains containing twins reduced significantly from 20.5% to 5.92% with Y addition. To explain the mechanism for the enhancement of the non-basal slip activity in Mg–Y alloy, the critical resolved shear stress of basal slip and pyramidal II slip were assessed by calculating τ max. The calculated results showed that the τ max ratio of the pyramidal II slip to basal slip decreased from 13.7 to 7.5, which may be responsible for the observed enhanced activity of non-basal slip. [ABSTRACT FROM AUTHOR]

Gas-gun experiments are carried out to study the mechanical properties and fracture behavior of a textured Mg–3Al–1Zn alloy under high strain rate. The impact direction (ID) is either perpendicular or parallel to crystallographic {0001} planes, referred to as ID ∥ 〈 c 〉 and ID ⊥ 〈 c 〉 , respectively. Shock compression and spallation are achieved with different specimen-to-flyer plate thickness ratios. The Hugoniot elastic limits and spall strengths are estimated as 0.32–0.35 GPa and 0.9–0.92 GPa, respectively, showing weak anisotropy. The deformed specimens are characterized with scanning electron microscope and X-ray computed tomography. Abundant { 10 1 ̄ 2 } extension twins are activated and the strain hardening rate exhibits a sharp increase and then decrease for the ID ⊥ 〈 c 〉 specimen, while a small number of twins are observed and the hardening rate decreases monotonically for the ID ∥ 〈 c 〉 specimen. As a result of the anisotropic distribution of the β -Mg 17 Al 12 phase, cracks are generally distributed in the mid-part and connected together for the ID ⊥ 〈 c 〉 case, while the distribution of cracks in the ID ∥ 〈 c 〉 specimen is relatively discrete along the ID and parallel to the rolling plane. [ABSTRACT FROM AUTHOR]

In previously published research, creep resistance of commercial alloy Elektron21 (El21) and El21 + 1% AlN/Al nanocomposite were predominantly investigated in as-cast condition, little work focused on creep resistance following heat treatment. In this work, El21 and its nanocomposite with and without T6 treatment (520 °C for 8 h and 200 °C for 16 h) were prepared to reveal the influence of heat treatment on their microstructural evolutions and creep properties. Different intermetallic particles and precipitates that formed in El21 and El21 + 1% AlN/Al with different states were characterized using optical microscopy (OM), X-ray diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscopy (TEM). Creep tests were performed over a stress range of 80–140 MPa at 240 °C. Creep results showed that the application of T6 treatment could improve the creep resistance of El21, but deteriorate that of El21 + 1% AlN/Al. This is attributed to the reduced amount of γ'' and β′ precipitates in El21 + 1% AlN/Al (T6) after ageing, resulting from the formation of plate-like Al 2 (Nd, Gd) (Al 2 RE) precipitates. It is also found that after T6 heat treatment, El21 (T6) had a lower minimum creep rate with a shorter duration of secondary creep stage than El21 + 1% AlN/Al (T6) at high creep temperatures due to the overageing of precipitates and the thermal stability of the Al 2 RE particles. El21 + 1% AlN/Al nanocomposites, either in the as-cast or T6 condition, show a much longer duration of secondary creep than NP-free El21. The responsible mechanism was attributed to the addition of AlN NPs and the formation of particulate/plate Al 2 RE phase. [ABSTRACT FROM AUTHOR]